The clinical introduction of penicillin in the 1940s is a milestone in the history of mankind since it led to a drastic decrease of the mortality rate caused by bacterial infections and also to an unprecedented improvement in the quality of life. The two decades between 1940 and 1960 have been defined as the “golden era of antibiotics” in which several new classes of antibiotics were developed and introduced on the market. Many life-threatening diseases became easily curable and the number of deaths or disabilities due to infectious diseases was drastically decreased. However, over the years bacteria exposed to antibiotics developed a large array of mechanisms of resistance, including modification of the drug target, molecular bypass, active efflux (or decreased entry) and chemical modification of the compound. As a consequence the 20 commonly used antibiotics are becoming less and less effective and the spread of multi-drug resistant bacteria is becoming a major threat for public health. Thus, the need for new antibiotics, with novel structures and/or mechanism of action, becomes more pressing every year.